Optical imaging systems may be employed as standalone hardware devices or integrated into other types of devices. For instance, still and video cameras are now regularly included in wireless computing devices (e.g., smartphones and tablets), laptop computers, video game interfaces, home automation devices, and even automobiles and other types of vehicles.
Optical imaging systems include image sensors that may utilize millions of sensor elements, or more. Sensor elements may malfunction due to fabrication imperfections or other factors. For example, some sensor elements may provide permanent or intermittent high, low, or fixed values independent of the light impinging on them through the optical imaging system. Some sensor elements may report values that are proportional to incident light, but that are corrupted by excessive levels of light-independent signal accumulating in the element during the exposure time. Furthermore, sensor elements may become occluded by, for example, a dust particle. The output of such sensor elements may lead to corresponding “dead,” “stuck,” “hot,” or obstructed pixels in images captured by the optical imaging system.
Image calibration processes may be performed to identify such abnormal sensor elements to make it possible to reduce or remove the effect of such image-degrading effects. For example, a camera calibration process may include capturing an image with a lens cap over the optical path to more easily identify “hot” pixels from a dark background image. However, such calibration processes may be limited to factory testing, may require the interaction of a user and/or may only be limited to identification of hot pixels.